1. Field of the Invention
The present invention relates to a semiconductor memory device using a variable resistance element or a phase-change element as a memory element. For example, the present invention relates to a resistance-change memory.
2. Description of the Related Art
In recent years, as an electrically rewritable nonvolatile semiconductor memory device, a resistive RAM (ReRAM) using a variable resistance element as a memory element or a resistance-change memory such as a phase-change RAM (PCRAM) using a phase-change element as a memory element has attracted attention as a succession memory of a flash memory.
In the resistance-change memory, for example, a variable resistance element and a rectifier element such as a diode are stacked on each of cross points of bit lines and word lines to make it possible to configure cell arrays. For this reason, a three-dimensional stacked memory in which a memory capacity can be increased can be formed without increasing a cell array portion in area.
The resistance-change memory finally has a structure in which oxide films are buried in areas between a large number of pillars obtained by stacking variable resistance elements and diodes. The variable resistance element is configured by a variable resistance material/electrode such as an electrode/metal oxide (two- or three-dimensional system).
However, in the structure described above, impurities such as fluorine and hydrogen to be diffused from the inside of an oxide film serving as the buried material into the variable resistance material. It may degrade the characteristics of the variable resistance material. For this reason, a structure in which a side surface of the variable resistance material is covered with a silicon nitride film to suppress the impurities such as fluorine and hydrogen from being diffused is proposed (for example, see Jpn. Pat. Appln. KOKAI Publication No. 2009-123900).
However, when such a silicon nitride film is formed on the side surface of a silicon diode serving as a rectifier element, reverse current increases and degrades the characteristics of the rectifier element.